1. Field of the Invention
This invention relates to a detection plate comprising an electronic circuit capable of being activated by a suitable interrogation field to generate a pre-determined signal, said plate having pin-shaped attachment means.
2. Description of Related Art
Such detection plates can be used in various situations. One known application of such detection plates or tags is in anti-shop-lifting systems. The articles to be protected are then each provided with a tag which is secured with a pin-shaped member to the articles to be protected. In the vicinity of the exits of the shop, a detector is installed, which generates a suitable interrogation field. Normally the tag is removed by shop attendants at the pay desk. If this is not done, the tag is activated by the interrogation field at an exit, and a signal is generated which can be detected by the detector. This signal may be a coded signal, but in the case of anti-shop-lifting systems is mostly composed of one or a few pre-determined frequencies.
Detection plates of the kind described can also be used in automating certain operations. Thus articles may, for example, be provided with a label which in a suitable interrogation field generates a specific code signal. This code may, for example, be recognized in a reading station, whereafter it can be determined in what manner this specific article is to be further treated. The further treatment may include, for example, a sorting action, a special operation, etc.
Detection plates of the kind described can also be used for the automatic recognition of cattle. Each animal is then provided with a tag, mostly taking the form of an earmark, which in a suitable interrogation field generates a specific code. The animal can thus, for example, be automatically recognized at a feeding trough, whereafter it is administered a pre-determined quantity of food under the control of a computer program.
Now, in all these cases, a non-authorized person can destructively remove the label or tag, although often with much difficulty, as result of which the animal or article concerned can no longer be automatically recognized when it passes the detector provided for the purpose. This is usually highly undesirable in conducting the operations in question, and in addition creates possibilities of fraud such as, in the example first mentioned, shop-lifting. In the last-mentioned example, fraud would be possible by, for example, transferring the specific earmark from a valuable animal to the ear of an animal of inferior quality, and subsequently selling the latter animal at too high a price.